DEL RIO, Texas, Sept 24 (Reuters) - An impromptu border camp that roiled the U.S. government was cleared of thousands of Haitian migrants by Friday, with most remaining in the United States for now and others expelled on deportation flights or returned to Mexico. Reuters witnesses said the jumble of makeshift shelters and tents had all but disappeared from Del Rio, Texas, with workers removing the last debris along the border with Mexico. State troopers lined the banks of the Rio Grande to discourage new crossings. U.S. Department of Homeland Security Secretary Alejandro Mayorkas said nearly 30,000 migrants had been encountered in Del Rio in the past two weeks and that by morning there were none left in the camp beneath its international bridge. Mayorkas vowed a swift probe into "horrifying" images that had sparked outrage this week which showed a border guard on horseback using his reins to contain Haitian migrants. "We know that those images painfully conjured up the worst elements of our nation"s ongoing battle against systemic racism," he told a news conference. More than 12,000 migrants will have a chance to make their case for protection before U.S. immigration judges, an estimated 8,000 voluntarily returned to Mexico, and 2,000 were expelled to Haiti. The fate of others detained is to be decided. Seeking to balance outrage about treatment of the migrants, Del Rio Mayor Bruno Lozano praised agents for trying to provide food and medical care, and said there were no fatalities. As well as the Biden administration"s decision to send migrants back to chronic instability convulsing Haiti, Mexico has sought to bus and fly Haitians to its southern states. On Friday, Reuters reported that the International Organization for Migration (IOM) had formally asked Brazil to receive some of the Haitians from the camp, according to two sources with knowledge of the request. read more Many of the Haitians arriving at the U.S. border had previously lived in Brazil and Chile, while others have transited through the South American countries. U.S. President Joe Biden has faced criticism over the expulsions, including in a sternly worded resignation letter from the U.S. Special Envoy to Haiti, Daniel Foote, who described the Caribbean nation as a collapsed state. Washington in May extended temporary protection from deportation to Haitians in the United States, citing political crisis, rights abuses, crime and lack of access to food, water and healthcare in the deeply impoverished country. Since then, Haiti"s president has been assassinated and it suffered a destructive earthquake. But the Biden government has kept up deportations, mindful that letting in more Haitians may encourage others to try. At least five more flights from the U.S. border were scheduled on Friday, flight tracking website FlightAware showed. Thousands more Haitians are moving through Central America, with others among around 16,000 awaiting boats into the jungles of the Darien Gap in Panama, a bottleneck on the journey north. Not all migrant traffic is U.S.-bound. On Friday, around 100 mostly Venezuelan migrants were moving south into Chile"s northern border in a bid to make a fresh start there. PUSHED SOUTH Haitians who crossed back to Mexico in recent days were met by Mexican officials who urged them to return to Mexico"s southern border with Guatemala to request asylumthere. "We"re not taking them out of the country," Francisco Garduno, head of the Mexican government"s National Migration Institute (INM), told Reuters. "We"re bringing them away from the border so there are no hygiene and overcrowding problems." Mexico"s Commission for Refugee Assistance (COMAR) is overwhelmed and scheduling appointments months away. Official data show Haitians are less likely to have asylum claims approved in Mexico compared with many nationalities. Last year, of all asylum claims that were formally resolved, only 22% of Haitian cases won approval, compared with 98% for Venezuelans, 85% of Hondurans, 83% of Salvadorans and 44% of Cubans. So far this year, the Haitian number is up to 31%. Willy Jean, who spent two fruitless months in the Mexican city of Tapachula, said if Mexico really wanted to help, it should allow them to make their applications elsewhere. "Tapachula"s really tough, really small, there"s lots of people," he told an INM agent trying to persuade him to go south. "There"s no work, there"s nothing."